package com.alg.queue;

/**
 * @author sc
 * Created on  2018/9/29
 */
public class LoopQueue<E> implements Queue<E> {
    private E[] data;
    private int front,tail;
    private int size;

    public LoopQueue(int capacity){
        data = (E[]) new Object[capacity+1];
        front=0;
        tail=0;
        size=0;
    }

    public LoopQueue(){
        this(10);
    }

    public int getCapacity(){
        return data.length-1;
    }

    @Override
    public int getSize() {
        return size;
    }

    @Override
    public boolean isFull() {
        return (tail+1)%(data.length)==front;
    }

    @Override
    public void enqueue(E e) {
        if(isFull()){
            resize(getCapacity()*2);
        }
        data[tail]=e;
        tail=(tail+1)%data.length;
        size++;
    }

    private void resize(int c) {
      E[] newData = (E[]) new Object[c+1];
        for (int i = 0; i < size; i++) {
            newData[i]=data[(front+i)%data.length];
        }
        data=newData;
        front=0;
        tail=size;
    }

    @Override
    public E dequeue() {
        if(isEmpty()){
           throw new IllegalArgumentException("can not dequeue from empty queue");
        }
        E ret = data[front];
        data[front]=null;
        front=(front+1)%data.length;
        size--;
        if(data.length==getCapacity()/4){
            resize(getCapacity()/2);
        }
        return ret;
    }

    @Override
    public E getFront() {
        if(isEmpty()){
            throw new IllegalArgumentException("can not dequeue from empty queue");
        }
        return data[front];
    }


    @Override
    public boolean isEmpty() {
        return front==size;
    }


}
